Apparatus and method for modem wake-up with autobaud function

Abstract

An apparatus and method for a data communications device, such as a modem, having a sleep mode for conserving energy and an operational mode for data transmission, to transition from the sleep mode to the operational mode. The wake up method and apparatus respond to the receipt of serial data from a terminal, including response to existing terminal commands. The wake up method and apparatus also autobauds to the serial data transmit signal. The wake up and autobauding operations occur in a way that are transparent to the user.

We claim: 
     
       1. In an arrangement of a data communication device for coupling to a terminal, the terminal having a data line for sending serial data to the data communication device, the terminal further having a terminal baud rate and a terminal baud time T B , the data communication device having a data communication device operational mode and further having a data communication device sleep mode, a wake up apparatus whereby the data communication device transitions from the data communication device sleep mode to the data communication device operational mode, the wake up apparatus comprising: a serial communications controller coupled to the data line for monitoring the serial data, the serial communications controller having means for determining an occurrence of a start bit and further having means for generating an interrupt signal in response to the occurrence of the start bit within a first predetermined time period T i  ; and   a second controller coupled to the data line, the second controller having means for receiving the interrupt signal, the second controller further having means to transition from a low power mode to a second controller operational mode in response to the interrupt signal within a second predetermined time period T w , and the second controller further having means to execute instructions to prepare for autobauding to a serial transmit data signal, within a third predetermined time period T p , wherein an arithmetic sum of the first, second and third predetermined time periods (T i , T w  and T p , respectively) is less than 1.5 times the terminal baud time T B  of the terminal baud rate ((T i  +T w  +T p )<(1.5)T B ).   
     
     
       2. The wake up apparatus of claim 1, wherein the start bit is followed by a binary sequence for an AT command signal. 
     
     
       3. The wake up apparatus of claim 1, the second controller further having means to reactivate a data pump. 
     
     
       4. In an arrangement of a data communication device for coupling to a terminal, the terminal having a data line for sending serial data to the data communication device, the terminal further having a terminal baud rate and a terminal baud time T B , the data communication device having a data communication device operational mode and further having a data communication device sleep mode, a wake up method whereby the data communication device transitions from the data communication device sleep mode to the data communication device operational mode, the wake up method comprising: (a) determining an occurrence of a start bit in the serial data;   (b) generating an interrupt signal within a first predetermined time period (T i ) following said determination; and   (c) transferring the data communication device from the data communication device sleep mode to the data communication device operational mode in response to the interrupt signal by transitioning a controller from a low power mode to a controller operational mode within a second predetermined time period (T w ) following said generation of the interrupt signal, and by executing instructions to prepare for autobauding to a serial transmit data signal within a third predetermined time period (T p ), wherein an arithmetic sum of the first, second and third predetermined time periods (T i , T w  and T p , respectively) is less than 1.5 times the terminal baud time T B  of the terminal baud rate ((T i  +T w  +T p )<(1.5)T B ).   
     
     
       5. The method of claim 4, wherein the start bit is followed by a binary sequence for an AT command signal. 
     
     
       6. The method of claim 4, further comprising: starting an autobaud routine for determining the baud rate of the serial data.   
     
     
       7. The method of claim 4, further comprising: reactivating a data pump.   
     
     
       8. In an arrangement of a data communication device for coupling to a terminal, the terminal having a data line for sending serial data to the data communication device, the terminal further having a terminal baud rate and a terminal baud time T B , the data communication device having an operational mode and further having a sleep mode, a wake up method whereby the data communication device transitions from the sleep mode to the operational mode, the wake up method comprising: (a) determining an occurrence of a start bit in the serial data;   (b) generating an interrupt signal within a first predetermined time period (T i ) following said determination;   (c) transitioning a controller from a low power mode to a controller operational mode within a second predetermined time period (T w ) following said generation of the interrupt signal;   (d) executing instructions to prepare for autobauding to a serial transmit data signal, within a third predetermined time period (T p ) following said transition;   (e) performing steps (b), (c) and (d) within a total time period less than 1.5 times the baud time T B  of the terminal baud rate; and   (f) reactivating a data pump.   
     
     
       9. In an arrangement of a data communication device for coupling to a terminal, the terminal having a data line for sending serial data to the data communication device, the terminal further having a terminal baud rate and a terminal baud time T B , the data communication device having a data communication device operational mode and further having a data communication device sleep mode, a method of transitioning the data communication device from the data communication device operational mode to the data communication device sleep mode, the method comprising: (a) configuring a serial communications controller for a predetermined response time;   (b) enabling second controller interrupts for incoming signals;   (c) disabling second controller interrupts for non-incoming signals; and   (d) instructing the second controller to enter a low power mode, wherein a total delay time for a transition from the data communication device sleep mode to the data communication device operational mode is less than 1.5 times the terminal baud time T B .   
     
     
       10. The method of claim 9 wherein step (b) further comprises enabling second controller interrupts for incoming ring, incoming transmit data, and DTE status changes. 
     
     
       11. The method of claim 9 wherein step (c) further comprises disabling second controller interrupt for periodic timers. 
     
     
       12. The method of claim 11 wherein step (a) further comprises: (a1) setting a UART baud rate to its maximum;   (a2) setting a data bits parameter of the serial communications controller to its minimum; and   (a3) enabling a break/abort interrupt of the serial communications controller.   
     
     
       13. The method of claim 12 wherein step (d) further comprises setting an input-output stop bit. 
     
     
       14. In an arrangement of a data communications device for coupling to a terminal, the terminal having a data line for sending serial data to the data communication device, the terminal further having a terminal baud rate and a terminal baud time T B , the data communication device having a data communication device operational mode and further having a data communication device sleep mode, a wake up apparatus whereby the data communication device transitions from the data communication device sleep mode to the data communication device operational mode, the wake up apparatus comprising: a serial communications controller having monitoring means for monitoring the serial data, the monitoring means having means for recognizing an occurrence of a start bit and further having means for generating an interrupt signal in response to the presence of the start bit within a first predetermined period of time T i  ; and   a second controller coupled to the data line, the second controller having means for receiving the interrupt signal, the second controller further having means for transferring from a low power mode to a second controller operational mode in response to the interrupt signal within a second predetermined time period T w , and the second controller further having means to execute instructions to prepare for autobauding to a serial transmit data signal, within a third predetermined time period T p , wherein an arithmetic sum of the first, second and third predetermined time periods (T i , T w  and T p , respectively) is less than 1.5 times the terminal baud time T B  of the terminal baud rate (T 1  +T w  +T p )<(1.5)T B .   
     
     
       15. In an arrangement of a data communications device for coupling to a terminal, the terminal having a data line for sending serial data to the data communication device, the terminal further having a terminal baud rate and a terminal baud time T B , the data communication device having a data communication device operational mode and further having a data communication device sleep mode, a wake up apparatus whereby the data communication device transitions from the data communication device sleep mode to the data communication device operational mode, the wake up apparatus comprising: a serial communications controller having monitoring means for monitoring the serial data, the monitoring means having means for recognizing an occurrence of a start bit and further having means for generating an interrupt signal in response to the presence of the start bit; and   a second controller coupled to the data line, the second controller having means for receiving the interrupt signal, the second controller further having means for transferring from a low power mode to a second controller operational mode in response to the interrupt signal, wherein a total delay time T a  for a transition from the data communication device sleep mode to the data communication device operational mode is less than 1.5 times the terminal baud time T B .   
     
     
       16. The wake up apparatus of claim 15, wherein the serial communications controller further has means to send the interrupt signal to the controller within a first predetermined time period T i , and wherein the second controller further has means to transition from the low-power mode to the second controller operational mode within a second predetermined time period T w  and to execute instructions to prepare for autobauding to a serial transmit data signal within a third predetermined time period T p . 
     
     
       17. The wake up apparatus of claim 16, wherein the total delay time T a  is an arithmetic sum of the first, second and third predetermined time periods (T a  =(T i  +T w  +T p )) and is less than 1.5 times the terminal baud time T B  of the terminal baud rate ({T a  =(T i  +T w  +T p )}<(1.5)T B ).